Do my suppliers need a Shopify account or a login?

No. Each supplier gets a private link. Whoever has the link sees that supplier's open orders, and you can replace the link at any time.

Can a supplier see other suppliers' items or my prices?

No. The portal shows only the items assigned to that supplier, with SKUs and quantities. Prices and other suppliers' items aren't shown.

What happens if the order is cancelled?

If the supplier has already been emailed, SplitFlow sends it a cancellation notice asking it not to ship, and the order disappears from its portal.

What if I ship some items myself?

Items that are fulfilled another way disappear from the supplier's list. SplitFlow never fulfills the same item twice.

How to send Shopify orders to your suppliers automatically

When you dropship with your own suppliers, every order has to reach the right supplier: which items, how many, and where they go. Forwarding each order by hand is slow, and the supplier often sees items and prices that belong to someone else.

Short answer: Shopify can email a copy of every order to any address, and Shopify Flow can email a fixed address when an order contains a supplier's products. In both cases the supplier sees the whole order, and someone still copies its tracking number into Shopify. If your supplier also sells on Shopify, Shopify Collective connects your stores directly. Otherwise, give each supplier a private link that shows only its own items, where it adds the tracking number itself.

Option 1: forward every order (built into Shopify)

In Settings → Notifications → Staff notifications, click Add recipient and enter the supplier's email address. From then on the supplier gets every new order — the whole order, including other suppliers' items, your prices and the customer's details. When the supplier sends you a tracking number, you add it to the order yourself.

Option 2: a Shopify Flow workflow

Shopify Flow can start a workflow when an order is created, check whether it contains a supplier's products (for example by vendor), and send an email to a fixed address with the Send internal email action. You decide what the email says, so it can list just that supplier's items. Tracking still comes back by email and has to be added to the order by hand.

Option 3: Shopify Collective, if your supplier is on Shopify

If your supplier also runs a Shopify store, check whether Shopify Collective is available to both of you. Orders for products you import from the supplier then go to the supplier's own admin, and the tracking number comes back to your store automatically. It only works with suppliers who sell on Shopify.

Option 4: a private supplier link with SplitFlow

Install SplitFlow from the Shopify App Store and open Suppliers.
Under Add a supplier, enter the supplier's name, up to three email addresses and the language for its emails and portal (English, German or Spanish).
Under Items this supplier ships, set a condition — usually Vendor equals the supplier's name. SKU, product tag and product type work too.
Choose when suppliers are emailed: once the order is paid (recommended) or as soon as it's placed.

For every new order with that supplier's items, SplitFlow emails the supplier a list of its items and a private link. In the portal the supplier sees its open orders — only its own items, with SKUs and quantities, no prices. It enters the tracking number, picks the carrier and clicks Mark as shipped. SplitFlow then marks exactly those items as fulfilled in Shopify, with the tracking, and Shopify sends the customer its shipping confirmation. You can turn that confirmation off in the supplier settings.

Good to know

The emails contain no customer details. Everything sits behind the private link, and New link replaces it at any time, so an old link stops working.
The portal also shows where the order goes: the customer's name and shipping address, plus the phone number if the order has one. SplitFlow reads them live from Shopify and doesn't store them.
It works whether or not the order was split. If you also split orders by vendor, each supplier's items are already in their own fulfillment.
The Free plan includes one supplier, Starter five, and Growth and Pro any number.

Questions

Do my suppliers need a Shopify account or a login?: No. Each supplier gets a private link. Whoever has the link sees that supplier's open orders, and you can replace the link at any time.
Can a supplier see other suppliers' items or my prices?: No. The portal shows only the items assigned to that supplier, with SKUs and quantities. Prices and other suppliers' items aren't shown.
What happens if the order is cancelled?: If the supplier has already been emailed, SplitFlow sends it a cancellation notice asking it not to ship, and the order disappears from its portal.
What if I ship some items myself?: Items that are fulfilled another way disappear from the supplier's list. SplitFlow never fulfills the same item twice.